Computer-controlled devices for detecting optical transmission and/or remittance properties of a measuring object such as densitometers or spectrophotometers are widely known. They can either be installed in fixed manner in a pressure contrivance or designed as mobile hand-held devices. Such a hand-held device in the form of a hand-held densitome meter is known from European Patent EP-A-0,603,448. This hand-held densitometer comprises a measuring unit for receiving the light transmitted by the measuring object (e.g., a printed sheet) and/or remitted from the measuring object. Furthermore, an exemplary hand-held device described therein has an input unit that is designed as a handwheel. With the help of this handwheel, for example, the type of measurement can be input (density measurement, tonal value determination, etc.), specific parameters of the measurement can be input, the measurement can be triggered, and so forth. In the case of other hand-held devices of this type, it is also common to input such features and/or to trigger the measurement with the help of a keyboard provided on the ha hand-held device naturally comprises a display unit (e.g., an LCD display) for displaying the values measured and, as before, for displaying the selected type of measurement, the parameters, etc.
On the inside, such devices typically also have a non-volatile memory (e.g., a ROM) in which the individual measuring functions of the device are stored. These measuring functions stored in the non-volatile memory are accessed during operation of the device in such a way that all measuring functions stored in this non-volatile memory are available to the user. At the same time, a control unit (control computer, microcomputer) controls the sequence of all procedures in the device.
In principal, such devices can be equipped with a large number of measuring functions, such as density measurement, measurement of density differences, measurement of density increases, determination of pressure characteristics, determination of area coverage, contrast measurement, measurement of color shading errors, and many more measuring functions. However, the various users of such devices do not always need all of these measuring functions. Thus, when purchasing such devices, the users do not insist on the device having the unnecessary measuring functions, since in the first place, the better-equipped devices usually cost more, and secondly, the not so well-equipped devices are naturally easier to handle, since certain measuring functions are not offered as options at all and therefore cannot contribute to the user's confusion. For example, a typical printer needs the measuring functions of density, density increase and area coverage. A printing-system with high quality requirements, for example, needs the measuring functions of density, density increase, area coverage, pressure characteristic and area coverage. A processing establishment (such as a photographic film processing establishment), on the other hand, typically needs the measuring functions of density and density increase, for example. However, other users only need the measuring function of density. Still other customers do not yet know, when purchasing such a device, exactly what they will want to measure in the future, or due to a change in operation (e.g., higher quality requirements of a printing-system), additional values must suddenly be measured with such a device.
For this reason, different devices are obtainable that are equipped with various measuring functions. This is usually realized in such a way that at any given time, all the measuring functions (programs) that the device can execute are stored in the non-volatile memory (e.g., ROM). In the case of devices that can execute different measuring functions, different measuring functions (programs) are also stored in the ROM at any given time. In principle, this is a solution as to how devices with different measuring functions can be provided, while the unwanted measuring functions are not provided and thus cannot contribute to the user's confusion. However, this is disadvantageous in the production of the devices insofar as the ROMs for the devices must in each case be specifically programmed in such a way that only very specific measuring functions (programs) are stored in them. As a result, depending on the customer's wishes and/or depending on the type of device offered for sale, a special ROM must be programmed and produced, and thus the production of the various devices is relatively expensive.